As a rubber composition for an automobile tire, a rubber composition containing a conjugated diene-based polymer such as polybutadiene or a butadiene-styrene copolymer, and a reinforcing agent is used.
In recent years, with increased concern about an environmental problem, requirements of fuel cost-saving properties on an automobile have been increasing, and a rubber composition used in a tire for an automobile has also been required to be excellent in fuel cost-saving properties.
For example, as a polymer enhancing fuel cost-saving properties, and a polymer composition good in fuel cost-saving properties, JP-A 7-82422 has proposed a polymer obtained by living anion-polymerizing butadiene, styrene and dimethylaminomethylstyrene using alkyllithium as a polymerization initiator, and a polymer composition containing the polymer and carbon black. In addition, JP-A 2003-160603 has proposed a conjugated diene-based polymer in which one end of a polymer obtained by copolymerizing butadiene and styrene using alkyllithium as a polymerization initiator is modified with 1-(4-N,N-dimethylaminophenyl)-1-phenylethylene, and a polymer composition of the polymer and a reinforcing agent. JP-A 1-217047 has proposed a conjugated diene-based polymer in which one end of a polymer obtained by copolymerizing butadiene and styrene using alkyllithium as a polymerization initiator is modified with N-dimethylaminopropylacrylamide, and a polymer composition of the polymer and a reinforcing agent. JP-A 1-217011 has proposed a conjugated diene-based polymer in which one end of a polymer obtained by copolymerizing butadiene and styrene using alkyllithium as a polymerization initiator is modified with bis(dimethylamino)methylvinylsilane, and a polymer composition of the polymer and a reinforcing agent.